Excellent answers already given. Yep....the very old NTC or even earlier Big Cam Cummins 855 series are mechanical mill that are again...big, tall and heavy. But...if you like older stuff and if the mill will physically fit in your Bus Conversion...

Then the very old Big Cam Cummins MAY be a good candidate. Easy to get to over 500 hp and 1650 torque using cheap, (inexpensive) good used factory parts. With a little bit of injector, pump, intercooler, timing and turbo work, ...

Along with a big air cleaner and good exhaust, over 600 EASY "street" hp are available. Try www.pittsburgfuelinjection.net for some good stuff for the older stuff. I was going to do this with my old Crown...but didn't. HB of CJ

On an automatic it's probably a moot point but I got spoiled on 3406 Cat and S60 engines that use variable speed style governors. On those the tach basically follows your foot exactly. If you gave it half throttle you got exactly that many rpm every time. On a Cummins PT fuel system the only thing that was constant was idle speed or max speed. If there was no load on the engine, 1/4 throttle could give you 2100 rpm. Downshifting was a "stab and grab" operation and if you stabbed too hard you overshot your target rpm and not hard enough, came up short. It all made for some rough gear changes until you got your "timing" down right.

The Celect system on the M11 and N14 is almost as bad but for a different reason. Because the throttle lag is so bad, you tend to overfuel it and when it finally responds, the end result is the same.

I have a big cam Cummins in my Eagle and it has been a very good motor. The conversion is about 10 years old and has about 105000 miles on it. The motor has been trouble free. The last trip to Florida we but on 4600 miles and got 6.72 miles per gallon. There are a couple of problems with the motor you should know about. At cold start up they smoke a lot, mine does not have that problem because the Agua Hot keeps the motor nice and warm. The other problem is while going down the road the motor will smoke a little bit. The problem with that is the exhaust exits low and will stink up your toad. I pull a Jeep wrangle and about every 10 or 15 thousand miles we will completely clean the soot out of the inside of the Jeep. I have tried all kinds of things to correct this and I have found it is the nature of the beast. I have found it helps to give it all the air on the intake side. ( I have to large filter ). And keep it tuned helps a lot. The next bus will be an electronic motor 60 S.

I had a pre EGR 1995 12.7L S60 in a D3. Great engine. Gobs of torque between 1200 and 1800 rpm.

It is a cold blooded engine in the winter. It came with a Webasto from the factory, and it was needed. I drove it a few trips with it not working. Really smokey until it got to temperature, which takes a long time. And the temp falls back down really fast idling around town or sitting. Plus it is a great thing for pre-heating for nice easy start when it is cold out.

Rusty-it is entirely possible to get that big cam to stop smoking. It is a function of having the properly sized turbo to the fuel button you're running. In your case, you have too big a fuel button for your turbo-hence the sooty smoking. One of two things-run a smaller button (less fuel) which means less power, or get a turbo with a smaller hot housing so it spins up more providing more air hence less smoking. Your fuel mileage might go up also. Good Luck, TomC

The Allison World transmission (B500, HD4060, 4000HS-all the same) is a much better choice for transmission. Granted the HT740 is a bullet proof transmission and is a mechanical trans, but only has 4spds with 4th being direct drive. If you're running 12R-22.5 tires @ 485rpm, on a Series 60, your top sweet spot rpm of 1600 will get you a speed of 59mph. We used to gear the Series 60 trucks for 1600rpm at 75mph. With using the World transmission, to get that speed, you can run 4.11 gears. And since the first 4 gears of both the HT740 and 4000 series are basically the same, the startability with the World transmission using 4.11 instead of 3.36's is quite obvious. Besides, if you're putting in a different engine, most likely you'd use an electronic engine-which the Allison 4000 series will work just fine with. Good Luck, TomC

If you upgrade your trans to an Allison World you will need an axle ratio of 3.90-4.10 depending on tire size. 4.10's will get you 66 mph@1375 with 24.5 rubber with the World .64 OD or 3.90's with 22.5's.

I already have a bus with Series 60 and B500. I have 4.10 gearing and 24.5 rubber. My 2nd overdrive is locked out. Is it worth trying to get 2nd overdrive re-enabled? I would need to find someone who has the software that isn't an actual Allison dealer as Allison dealers won't make the change.

1600 gives you 66 mph with the .74 OD you have now. If you had 6th gear it would run the same speed at 1375. A little on the low side of happy for a DDEC3 if it was hauling 80,000 lbs but OK running 35-40,000 lbs IMHO. If you have a DDEC5 EGR mess it would be on the high side if not outside of the sweet spot for fuel economy as the EGR motors like to run about 1350 for best economy. With your current setup anything much over 60 mph is going to run you over 1500 and there goes your fuel even if it is a pre 98 engine.

What exactly is their excuse? I got the same runaround with Cummins when I jacked my N14 up to 525 hp/1850 torque. Said my trans was only rated for 1650 so they wouldn't do it. Last time I checked I OWN the engine AND the transmission and everything bolted to them. I took it to my local International dealer and they were more than happy to take my money. See if you can find an MCI or Prevost shop or a truck dealer like Freightliner or Western Star that is certified Allison and see if they will do it.

Belfert-since you want to cruise a Series 60 no faster then 1600 for best fuel mileage, your present setup of 5th gear will get you 66mph in 5th at 1600. So yes I'd have the 6th gear opened up. Then at 75mph, in 5th you'd be doing 1800 (which isn't bad for the engine-1800 is the continuous rpm rating of the Series 60-just not the best fuel mileage), and in 6th you'd be at 1556rpm at 75-perfect! Good luck, TomC

What exactly is their excuse? I got the same runaround with Cummins when I jacked my N14 up to 525 hp/1850 torque. Said my trans was only rated for 1650 so they wouldn't do it. Last time I checked I OWN the engine AND the transmission and everything bolted to them. I took it to my local International dealer and they were more than happy to take my money. See if you can find an MCI or Prevost shop or a truck dealer like Freightliner or Western Star that is certified Allison and see if they will do it.

The local Freightliner dealer and the local Detroit dealer are owned by the same folks. They told me some years back that the cost to change the setting to enable 6th gear would be $600. The kicker is they want a letter from an engineer at the original manufacturer stating it is okay to enable 6th gear.

I'm figuring a shop that isn't Allison authorized that has the proper gear could do it for way less money without a letter. I usually cruise at 65 MPH per GPS which puts me between 1500 and 1600 RPM.

If you want your ECU reprogramed to get the 6th gear it can be done for $100.00 plus shipping. You will need to get a cin number from one that has the same ECU with the same transmission and ship your ECU with the new number and $200.00 will get it done.

Back to the repower, I know that some don't like the series 50 engines. I think they are great and where else can you get a good world transmission, 4 stroke engine with all the wiring and parts for four to seven thousand dollars. If the engine blows, you can get just an engine for about $2,500. Another for the MCI you don't have to change anything to put the engine into the coach. The engine fits the same space as the 8v71 behind the drop down.

If you want to know where to get the ECU done give me a call 863-206-3838. no I don't do them myself.Jack

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There is NOTHING wrong with the Series 50. Yes it vibrates at idle, but if you use the proper engine mounts for the engine, it is really not that bad. The only real weak point of the engine is the twin counter rotating balancing shafts below the crankshaft. They need to be replaced every 300,000mi whether they need it or not. If that is done, it is a GREAT bus engine-almost guaranteeing you'll get 10mpg. Good Luck, TomC